387. First Unique Character in a String

Description

Given a string, find the first non-repeating character in it and return it's index. If it doesn't exist, return -1.

Examples:

s = "leetcode"
return 0.

s = "loveleetcode",
return 2.

Note: You may assume the string contain only lowercase letters.

Solution

/**
 * Solved with hash table
 * @param {string} s
 * @return {number}
 */
var firstUniqChar = function(s) {
    "use strict";
    let table = {};
    for (let i = 0; i < s.length; i++) {
        if (table[s[i]] === undefined) {
            table[s[i]] = 0;
        }
        table[s[i]]++;
    }
    for (let i = 0; i < s.length; i++) {
        if (table[s[i]] === 1) {
            return i;
        }
    }
    return -1;
};